Mack CF Posted March 13, 2006 Share Posted March 13, 2006 hi, the mack im looking to buy has a "slight" electrical problem, im not really sure what it is though. Its a 1966 B model mack. What happens is whenever a new set of batteries is thrown on the truck, they die within an day. Its been sitting due to this problem and will be up for sale around november, and its my only real chance of getting a truck. Anyone know what kind of problem is causing this? and how much it could be to fix. Thanks alot! Quote Link to comment https://www.bigmacktrucks.com/topic/933-b-model-electrical-problem/ Share on other sites More sharing options...
DWaits Posted March 13, 2006 Share Posted March 13, 2006 hi, the mack im looking to buy has a "slight" electrical problem, im not really sure what it is though. Its a 1966 B model mack. What happens is whenever a new set of batteries is thrown on the truck, they die within an day. Its been sitting due to this problem and will be up for sale around november, and its my only real chance of getting a truck. Anyone know what kind of problem is causing this? and how much it could be to fix. Thanks alot!Do they run down with the truck just sitting and not running or do they run down with the truck running?DW Quote 1948 Mack Pumper Link to comment https://www.bigmacktrucks.com/topic/933-b-model-electrical-problem/#findComment-4772 Share on other sites More sharing options...
Mack CF Posted March 13, 2006 Author Share Posted March 13, 2006 Do they run down with the truck just sitting and not running or do they run down with the truck running?DWIm not exactly sure, all he told me was that when they throw new batteries on it, their both dead within a day. I assume it comes from sitting, but im not 100% sure. I guess all possible scenarios would help. If they died while its running, it would be a problem within the generator/alternator. If they die while its sitting, im not sure. Quote Link to comment https://www.bigmacktrucks.com/topic/933-b-model-electrical-problem/#findComment-4774 Share on other sites More sharing options...
Brian Posted March 14, 2006 Share Posted March 14, 2006 Mack CF if your batteries are going dead while the truck is setting it more than likely has a drain somewhere. These can be hard to find. One way to stop this is with a battery disconnect switch, the come either with or without keys, and cost about 50 bucks if I remember right for the switch and cable ends to hook it up. Hope this helps, Block. Quote Link to comment https://www.bigmacktrucks.com/topic/933-b-model-electrical-problem/#findComment-4781 Share on other sites More sharing options...
Mack CF Posted March 14, 2006 Author Share Posted March 14, 2006 Thanks, the truck does have a battery switch, an A-Off-B set up... i think theres a short somewhere in the truck and the power trickles out somewhere. thanks for help Quote Link to comment https://www.bigmacktrucks.com/topic/933-b-model-electrical-problem/#findComment-4782 Share on other sites More sharing options...
Rob Posted March 14, 2006 Share Posted March 14, 2006 Mack CF, this sounds like a welded set of contacts someplace. Could be the series/parallel switch, or the regulator assy. I would undo the "BAT" terminal from the regulator and see if the problem persists. If so, take a cable loose from each battery (one at a time) and check for voltage depletion every couple of hours. An internal shorted battery usually is abnormally warm to the touch. I would lean on the regulator first.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/933-b-model-electrical-problem/#findComment-4783 Share on other sites More sharing options...
Mack CF Posted March 14, 2006 Author Share Posted March 14, 2006 Would a volt meter be able to pick it up if the battery is draining? Quote Link to comment https://www.bigmacktrucks.com/topic/933-b-model-electrical-problem/#findComment-4784 Share on other sites More sharing options...
ThaddeusW Posted March 14, 2006 Share Posted March 14, 2006 Would a volt meter be able to pick it up if the battery is draining?You need an ammeter to measure the drain current. The battery voltage will drop but its not the proper way to check for the leak. Try this get a 12V bulb and disconnect one of the main battery leads (make sure the series parallel switch is in 12V.) Put the bulb in series with the battery leads. If it glows or lights with the ignition off you have a leak somewhere. Try that and pull the fuses one by one until the lamp extinguishes, if that doesent work then your going to have to dig around and disconnect wires till you find the leak. You can use a volt meter to probe around for power while the ignition is off (leave one lead connected to a good ground point). A dead short would melt any smaller gauge wires. IF the batteries die in one night then its a major leak as 4 12v truck batteries dont die so easily from obvious things like lights or radio left on. Quote -Thad What America needs is less bull and more Bulldog! Link to comment https://www.bigmacktrucks.com/topic/933-b-model-electrical-problem/#findComment-4785 Share on other sites More sharing options...
Mack CF Posted March 14, 2006 Author Share Posted March 14, 2006 Thanks for all your help so far! Quote Link to comment https://www.bigmacktrucks.com/topic/933-b-model-electrical-problem/#findComment-4786 Share on other sites More sharing options...
Freightrain Posted April 3, 2006 Share Posted April 3, 2006 A test light in series with neg or pos cable will tell if you found the draw. Leave light hooked up and go around unhook stuff til the light goes out. Presto-chango the problem will be solved. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/933-b-model-electrical-problem/#findComment-5230 Share on other sites More sharing options...
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